An acrostic is a poem (or other form of writing) in which the first letter (or syllable, or word) of each line (or paragraph, or other recurring feature in the text) spells out a word, message or the alphabet.[1] The word comes from the French acrostiche from post-classical Latinacrostichis, from Koine Greek ἀκροστιχίς, from Ancient Greek ἄκρος "highest, topmost" and στίχος "verse").[2] As a form of constrained writing, an acrostic can be used as a mnemonic device to aid memory retrieval.

Relatively simple acrostics may merely spell out the letters of the alphabet in order; such an acrostic may be called an 'alphabetical acrostic' or Abecedarius. These acrostics occur in the first four of the five songs that make up the Book of Lamentations, in the praise of the good wife in Proverbs 31, 10-31, and in Psalms25, 34, 37, 111, 112, 119 and 145 of the Hebrew Bible.[3] Notable among the acrostic Psalms is the long Psalm 119, which typically is printed in subsections named after the 22 letters of the Hebrew alphabet, each section consisting of 8 verses, each of which begins with the same letter of the alphabet and the entire psalm consisting of 22 x 8 = 176 verses; and Psalm 145, which is recited three times a day in the Jewish services. Some acrostic psalms are technically imperfect. E.g. Psalm 9 and Psalm 10 appear to constitute a single acrostic psalm together, but the length assigned to each letter is unequal and five of the 22 letters of the Hebrew alphabet are not represented and the sequence of two letters is reversed. In Psalm 25 one Hebrew letter is not represented, the following letter (Resh) repeated. In Psalm 34 the current final verse, 23, does fit verse 22 in content, but makes line too long. In Psalms 37 and 111 the numbering of verses and the division into lines are interfering with each other; as a result in Psalm 37, for the letters Daleth and Kaph there is only one verse, and the letter Ayin is not represented. Psalm 111 and 112 have 22 lines, but 10 verses. Psalm 145 does not represent the letter Nun, having 21 one verses, but one Qumran manuscript of this Psalm does have that missing line, which agrees with the Septuagint. Acrostics prove that the texts in question were originally composed in writing, rather than having existed in oral tradition before being put into writing.

Acrostics are common in medieval literature, where they usually serve to highlight the name of the poet or his patron, or to make a prayer to a saint. They are most frequent in verse works but can also appear in prose. The Middle High German poet Rudolf von Ems for example opens all his great works with an acrostic of his name, and his world chronicle marks the beginning of each age with an acrostic of the key figure (Moses, David, etc.). In chronicles, acrostics are common in German and English but rare in other languages.[4]

Often the ease of detectability of an acrostic can depend on the intention of its creator. In some cases an author may desire an acrostic to have a better chance of being perceived by an observant reader, such as the acrostic contained in the Hypnerotomachia Poliphili (where the key capital letters are decorated with ornate embellishments). However, acrostics may also be used as a form of steganography, where the author seeks to conceal the message rather than proclaim it. This might be achieved by making the key letters uniform in appearance with the surrounding text, or by aligning the words in such a way that the relationship between the key letters is less obvious. This is referred to as null ciphers in steganography, using the first letter of each word to form a hidden message in an otherwise innocuous text.[5] Using letters to hide a message, as in acrostic ciphers, was popular during the Renaissance, and could employ various methods of enciphering, such as selecting other letters than initials based on a repeating pattern (equidistant letter sequences), or even concealing the message by starting at the end of the text and working backwards.[6]

There is an acrostic secreted in the Dutch national anthem Het Wilhelmus[7] (The William): the first letters of its fifteen stanzas spell WILLEM VAN NASSOV. This was one of the hereditary titles of William of Orange (William the Silent), who introduces himself in the poem to the Dutch people. This title also returned in the 2010 speech from the throne, during the Dutch State Opening of Parliament, whose first 15 lines also formed WILLEM VAN NASSOV.

An acrostic poem written in English by Edgar Allan Poe is entitled simply "An Acrostic":[8]

Elizabeth it is in vain you say
"Love not"—thou sayest it in so sweet a way:In vain those words from thee or L.E.L.Zantippe's talents had enforced so well:Ah! if that language from thy heart arise,Breath it less gently forth—and veil thine eyes.Endymion, recollect, when Luna triedTo cure his love—was cured of all beside—His follie—pride—and passion—for he died.

James May, presenter on the BBC program Top Gear, was fired from the publication Autocar for spelling out a message using the large red initial at the beginning of each review in the publication's Road Test Yearbook Issue for 1992. Properly punctuated, the message reads: "So you think it's really good? Yeah, you should try making the bloody thing up. It's a real pain in the arse."[11]

In the 2012 third novel of his Caged Flower[12] series, author Cullman Wallace used acrostics as a plot device. The parents of a protagonist send e-mails where the first letters of the lines reveal their situation in a concealed message.

In 2013 a school headmaster resigned after announcing the retirement of a teacher in a statement which began "We all now know every really great teacher has to finish one day..." The initial letters of the first six words caused offence.[13]

On August 23, 2017, University of California-Berkeley energy professor Daniel Kammen resigned from his position as a State Department science envoy with a resignation letter in which the word "IMPEACH" was spelled out by the first letters of each paragraph.[15]

In the video game Zork the first letters of sentences in a prayer spelled "Odysseus" which was a possible solution to a cyclops encounter in another room.[16]

Acrostics can be more complex than just by making words from initials. A double acrostic, for example, may have words at the beginning and end of its lines, as this example, on the name of Stroud, by Paul Hansford -

S et among hills in the midst of five valley S,
T his peaceful little market town we inhabi TR efuses (vociferously!) to be a conforme R.
O nce home of the cloth it gave its name t O,
U phill and down again its streets lead yo U.
D espite its faults it leaves us all charme D.

The first letters make up the acrostich and the last letters the telestich; in this case they are identical.

The poem Behold, O God!, by William Browne,[17] can be considered a complex kind of acrostic. In the manuscript, some letters are capitalized and written extra-large, non-italic, and in red, and the lines are shifted left or right and internally spaced out as necessary to position the red letters within three crosses that extend through all the lines of the poem. The letters within each cross spell out a verse from the New Testament:

The "INRI" at the top of the middle cross stands for Iēsus Nazarēnus, Rēx Iūdaeōrum, Latin for "Jesus of Nazareth, King of the Jews" (John 19:3). The three quotes represent the three figures crucified on Golgotha, as recorded in the gospels of Matthew and Luke.

(The text of the manuscript shown differs significantly from the text usually published, including in the reference.[17] Many of the lines have somewhat different wording; and while the acrostics are the same as far as they go, the published text is missing the last four lines, truncating the acrostics to "Lord, remember me when thou comest into thy kin", "O God, my God, why hast thou forsak", and "If thou art the Christ, save thyself". The manuscript text is printed below, first as normal poetry, then spaced and bolded to bring out the acrostics. The word "Thou" in line 8 is not visible in this photograph, but is in the published version and is included in a cross-stitch sampler of the poem from 1793.[18])

Behold, O God! In rivers of my tears
I come to thee! bow down thy blessed ears
To hear my Plaint; and let thine eyes which keep
Continual watch behold a Sinner weep:
Let not, O God my God my Sins, tho' great,
And numberless, between thy Mercy's-Seat
And my poor Soul have place; since we are taught,[Thou] Lord, remember'st thyne, if Thou art sought.
I come not, Lord, with any other merit
Than what I by my Saviour Christ inherit:
Be then his wounds my balm— his stripes my Bliss;
His thorns my crown; my death be blest in his.
And thou, my blest Redeemer, Saviour, God,
Quit my accounts, withhold thy vengeful rod!
O beg for me, my hopes on Thee are set;
And Christ forgive me, since thou'st paid my debt
The living font, the Life, the Way, I know,
And but to thee, O whither shall I go?
All other helps are vain: grant thine to me,
For in thy cross my saving health I see.
O hearken then, that I with faith implore,
Lest Sin and Death sink me to rise no more.
Lastly, O God, my course direct and guide,
In Death defend me, that I never slide;
And at Doomsday let me be rais'd again,
To live with thee sweet Jesus say, Amen.